1. Field of the Invention
The present invention relates to a method of manufacturing an optical component by die molding, and particularly to a production method in which an optical component is molded integrally with a holder.
2. Related Art
An optical component (or, optical element) such as a lens is often used while being housed in a holding member (holder) made of a metal or the like. The function of an optical component may be impaired by stain or scratch, and hence it is difficult to handle an optical component. When a holder is previously disposed, it is not required to handle an optical component with directly contacting the component, also in a step of incorporating the component into a machine or the like, so that occurrence of stain or scratch can be reduced.
In an optical component having an optical element and a holder in which the optical element such as a lens is made of glass, a resin, or the like and fixed into the holder, the holder and the optical element may be separately produced and then fixed together by adhesion. Alternatively, such an optical component having a holder is sometimes produced by a method in which a blank for the optical element is pressurized and deformed in the holder, and an optical surface is formed simultaneously with press fixation to the holder (for example, JP-A-61-114822 and JP-A-3-265529).
FIGS. 1A through 1D show a conventional procedure in the production of an aspherical lens by such a molding method. Hereinafter, the identical components are denoted by the same reference numerals, and their description may be often omitted. As shown in FIG. 1A, first, a lower die 12 is incorporated in a cylindrical barrel die 10 with upward directing a molding surface 15. In the lower die, a step 13 is formed, and a lower portion 14 has a larger diameter. A cylindrical inner sleeve 18 which is an auxiliary member is placed on the step 13. In this state, first, a lens holder 130 made of a metal is inserted from an upper portion of the barrel die 10, and placed at a predetermined position of the inner sleeve 18. As shown in FIG. 1B, then, a lens blank 120 is inserted into a through hole of the lens holder 130, and placed on the molding surface 15 of the lower die 12.
The lens blank 120 is made of a glass material, and processed into a spherical shape as shown in FIG. 2A. The lens holder 130 has a cylindrical shape as shown in FIG. 2B, and comprises a through hole having a circular section shape. The inner diameter B of the through hole must be larger than the diameter A of the lens blank 120. The relationship between A and B must be designed so that the lens after shaping is in close contact with the lens holder, and an excess of the blank is not produced.
In this state, as shown in FIG. 1C, an upper die 116 is inserted and lowered into the upper portion of the barrel die 10 to press the lens blank 120 which is softened by heating to a predetermined temperature. As a result of the above procedure, as shown in FIGS. 2A and 2B, a molded product 122 which is defined by the shapes of the lower and upper dies 12, 116 and the lens holder 130 is formed. The molded product 122 is fixed to the lens holder 130, but is not fixed to the lower and upper dies 12, 116 which are previously subjected to a releasing process, and can be released from the dies.
After the molding process is completed, as shown in FIG. 1D, the upper die is removed away, and an aspherical lens 150 having a holder is taken out. A holder and a lens blank are newly prepared, and the same procedure is conducted, whereby an aspherical lens having a holder can be repeatedly produced. According to this apparatus, only the upper die is taken out, and the other members are not required to be reassembled. Therefore, the repeated production is enabled within a short time period.
The lens holder is usually transported onto the inner sleeve while being mechanically grasped or sucked by vacuum suction. The lens holder 130 has the through hole 136. In order to mechanically grasp the lens holder, therefore, means such as that a tweezers-like grasping tool 160 grasps an outer peripheral portion 132 as shown in FIG. 3A, or that the tool outward pushes an inner peripheral portion 134 to hold the lens holder as shown in FIG. 3B is taken.
When vacuum suction is employed, a method such as that in which suction is conducted while a suction port 180 is in contact with a side face 132 as shown as shown in FIG. 3C, or that in which suction is conducted while the suction port is in contact with an end face 138 that is deviated from the center, and that has a small area is selected.
In the conventional method, the two transportation works of placing the lens holder onto the inner sleeve, and then transporting the lens blank to the lower-die surface in the through hole of the lens holder are required. Therefore, there is a problem in that the working efficiency is poor.
Each of the lens holder transporting methods shown in FIGS. 3A through 3D has a problem. In the method of FIG. 3A, the grasping tool 160 is placed outside the lens holder 130, and hence a room for allowing the grasping tool 160 to pass must be formed between the outer diameter of the lens holder 130 and the diameter of the inner periphery of the barrel die. The upper and lower dies and the like must be correspondingly produced in a larger size, and the cost of the production apparatus is increased. In the method of FIG. 3B, the lens holder is unstably held, and therefore easily drops during transportation.
In the case where the side face 132 of the lens holder 130 is sucked as shown in FIG. 3C, the lens holder must be rotated by 90° in the barrel die, and inadequate placement of the lens holder 130 as shown in FIG. 4 easily occurs. In the case of FIG. 3D, the suction port 180 must be inserted in close proximity to the inner peripheral face of the barrel die. Therefore, it is necessary to provide a room for the insertion, and the holding becomes easily unstable. In this case also, consequently, the problem such as shown in FIG. 4 readily occurs.